This invention relates to by-pass valves for use in the exhaust system of an automobile engine and, more specifically, to an improved by-pass valve incorporating overpressure protection.
With increasing use of catalytic converters, the system for introducing additional air into the converter at appropriate points and times, in order to obtain more complete combustion of the fuel and reduced emissions, has been modified to include a two-way switch valve. For the sake of convenience, cost, and space requirements in the engine compartment, the switch valve has been incorporated in the by-pass valve previously used in engine exhaust systems. The by-pass valve has been redesigned to accomplish this and a number of problems have arisen. One problem encountered involves overpressure protection in the event the selected switch valve output is blocked for some reason. When this occurs, it is necessary to dump air entering the by-pass valve to atmosphere or else the air pump used with the valve may be damaged or destroyed which will adversely effect operation of the catalytic converter.